For example, in semiconductor device fabrication process, a resist pattern is formed as a mask for forming a predetermined pattern by a so-called photolithography technology in which after a resist liquid is supplied to the top surface of a semiconductor wafer (hereinafter called “wafer”) to form a resist film, and an exposure process of a predetermined pattern is performed on a resist-coated wafer, an exposure pattern formed on the resist film on the wafer is developed.
In such a photolithography process, it is known to couple an exposure apparatus to a substrate processing system constructed in such a way as to integrate a plurality of modules which perform resist coating and development before and after exposure, baking, etc. and achieve space reduction, an improvement on the throughput, and the like (for example, Unexamined Japanese Patent Application KOKAI Publication No. 2001-345241).
While the substrate processing system in which a plurality of modules are integrated as mentioned above is provided with a transfer mechanism which transfers a substrate among individual modules, there are multifarious combinations of pre-processes and post-processes of exposure (i.e., modules) and process orders, and efficient control of the transfer mechanism which moves a control method among those modules becomes an important factor to determine the performance of the substrate processing system.
According to the conventional control method of the transfer mechanism in such a substrate processing system, the present positional information (in which module the substrate lies) is stored as management information of the transfer mechanism in a memory, and the next transfer position is decided each time based on a transfer recipe (information comprised of a combination of the modules and a sequential transfer order among modules). In the process of a complicated transfer recipe using a plurality of modules, therefore, there is a problem such that the substrate transfer timing cannot be predicted and the transfer time is significantly disturbed. This problem is particularly noticeable when the transfer recipe differs between a plurality of lots which are executed in order.
Because the substrate transfer timing cannot be predicted as mentioned above, there arises another problem such that it is difficult to process a plurality of lots in parallel without causing an inconvenience, such as passing a substrate between the lots, and in a case where a plurality of lots with different recipes are carried out consecutively, it is necessary to start a succeeding lot when the process of a preceding lot is completely finished, and the overall processing time becomes simple summation of the required times of the individual lots so that an improvement on the throughput cannot be expected.
As the module by which a substrate passes is not predetermined, feedforward control which predicts the future transfer timing of the substrate during a lot process and performs control is also difficult.
Further, as the transfer position of a substrate is determined every time, it is difficult for a system manager to visually grasp the transfer conditions of all the substrates in the unit of a lot, and there is room for improvement even from the viewpoint of operability.